Gabby Williams has the facial features and skin of a newborn, and she is just as dependent. Her mother feeds, diapers and cradles her tiny frame as she did the day she was born.

The little girl from Billings, Montana, is 8 years old, but weighs only 11 pounds. Gabby has a mysterious condition, shared by only a handful of others in the world, that slows her rate of aging.

For the past two years, a doctor who has been trying to find the genetic off-switch to stop the aging process has been studying Gabby, as well as two other people who have striking similarities.

A 29-year-old Florida man has the body of a 10-year-old, and a 31-year-old Brazilian woman is the size of a 2-year-old. Like Gabby, neither seems to grow older.

Unraveling what these three people may have in common is the subject of a TLC television special, "40-Year-Old Child: A New Case," which airs Monday, Aug. 19, at 10 p.m. ET. The show is a follow-up to Gabby's story, which aired last year.

"In some people, something happens to them and the development process is retarded," said medical researcher Richard F. Walker. "The rate of change in the body slows and is negligible."

Walker explains that physiological change, or what he calls "developmental inertia," is essential for human growth. Maturation occurs after reproduction.

"Without that process we never develop," he said. "When we develop, all the pieces of our body come together and change and are coordinated. Otherwise, there would be chaos."

But, said Walker, the body does not have a "stop switch" for this development. "What happens is we become mature at age 20 and continue to change."

The first subtle internal body changes of aging are seen in the 30s and become more visible in the 40s.

"There is a progressive erosion of internal order as a result of developmental inertia," he said.

In one of the girls Walker has studied, he found damage to one of the genes that causes developmental inertia, a finding that he said is significant. He also suspects the mutations are on the regulatory genes on the second female X chromosome.

"If we could identify the gene and then at young adulthood we could silence the expression of developmental inertia, find an off-switch, when you do that, there is perfect homeostasis and you are biologically immortal."

Gabby Williams has the facial features and skin of a newborn, and she is just as dependent. Her mother feeds, diapers and cradles her tiny frame as she did the day she was born.

The little girl from Billings, Montana, is 8 years old, but weighs only 11 pounds. Gabby has a mysterious condition, shared by only a handful of others in the world, that slows her rate of aging.

For the past two years, a doctor who has been trying to find the genetic off-switch to stop the aging process has been studying Gabby, as well as two other people who have striking similarities.

A 29-year-old Florida man has the body of a 10-year-old, and a 31-year-old Brazilian woman is the size of a 2-year-old. Like Gabby, neither seems to grow older.

Unraveling what these three people may have in common is the subject of a TLC television special, "40-Year-Old Child: A New Case," which airs Monday, Aug. 19, at 10 p.m. ET. The show is a follow-up to Gabby's story, which aired last year.

"In some people, something happens to them and the development process is retarded," said medical researcher Richard F. Walker. "The rate of change in the body slows and is negligible."

Walker explains that physiological change, or what he calls "developmental inertia," is essential for human growth. Maturation occurs after reproduction.

"Without that process we never develop," he said. "When we develop, all the pieces of our body come together and change and are coordinated. Otherwise, there would be chaos."

But, said Walker, the body does not have a "stop switch" for this development. "What happens is we become mature at age 20 and continue to change."

The first subtle internal body changes of aging are seen in the 30s and become more visible in the 40s.

"There is a progressive erosion of internal order as a result of developmental inertia," he said.

In one of the girls Walker has studied, he found damage to one of the genes that causes developmental inertia, a finding that he said is significant. He also suspects the mutations are on the regulatory genes on the second female X chromosome.

"If we could identify the gene and then at young adulthood we could silence the expression of developmental inertia, find an off-switch, when you do that, there is perfect homeostasis and you are biologically immortal."

Wow, this is quite incredible, It does leave me wondering if at say age 50 these people will have grown into "teenage" form and will live lives like normal people or if this is something that will never change for them. Does it also mean that let's say their aging process is half of a normal person, could they live till they were almost 200?

The last sentence scares me though "biologically immortal", reminds me of Torchwood: Miracle Day. I know it's not the same but certain aspects of that would rain true, population boom, resources being stretched far beyond what we can currently sustain etc. Not many people want to die, but I also don't like the idea of living forever.

Wow, this is quite incredible, It does leave me wondering if at say age 50 these people will have grown into "teenage" form and will live lives like normal people or if this is something that will never change for them. Does it also mean that let's say their aging process is half of a normal person, could they live till they were almost 200?

I believe in very high level way of looking at it, cancer is caused by the splitting/regeneration of cells, and those cells mutating in some way during this process. I would assume that because the rate of change in the body is so slow then this would be the same on a cellular level also.

Looking at the video, they all also appear to be quite severely disabled as well... Possibly it's connected to the retarded ageing.

Exactly.

While the proposition of a longer life is intriguing (i too would want to have this gene switched off at 25 and celebrate 26th birthday every year thereafter), it will come with a cost, some nasty side effect. So, no thanks.

I'd rather have a full-value life, than suffering with a disability for the eternity.

~Snip~ It does leave me wondering if at say age 50 these people will have grown into "teenage" form and will live lives like normal people or if this is something that will never change for them. Does it also mean that let's say their aging process is half of a normal person, could they live till they were almost 200? ~snip~

Very same question I was going to ask

In the hope there is an expert on biology, or this field specifically, does this happen? Do they live longer than whatever the average for the location is?